Which of the following actions is considered tampering with emissions controls?

Tampering with emissions controls refers to any action that modifies or removes components designed to reduce harmful emissions from an engine. Removing emissions control elements directly changes the way the engine operates concerning environmental standards, making it a clear violation of emissions regulations.

In contrast, performing routine maintenance is essential for keeping the engine running efficiently while still adhering to emissions standards and does not alter the emissions system. Using factory-recommended lubricants ensures the engine runs smoothly and efficiently without affecting emissions controls. Installing limiter caps, which can restrict engine performance to comply with regulations, does not modify or remove existing emissions controls but rather supports compliance. Therefore, the removal of emissions control elements stands out as the definitive act of tampering.